Dispensers are widely available for dispensing a variety of flowable materials including creams, lotions, soaps and pastes, all of which will be generally referred to as “soap.” These dispensers incorporate a variety of pumps including diaphragm pumps. In most cases, the diaphragm pump includes a base to which a flexible dome is attached to define a pumping chamber therebetween. The flexible dome component is used to create pressure to open an outlet valve and release product from the dispenser and also create a vacuum that opens an inlet valve to bring product back into the pump chamber.
Existing domes, generally have a continuous surface and are typically hemispherical in shape. As a result, the existing domes do not collapse in a repeatable consistent fashion. For example, sometimes, one side of the dome will collapse to a greater extent than another side upon application of the same force at the same location. These inconsistencies affect pump performance by creating dead spaces, where fluid is trapped behind the collapsed portion of the dome and cannot escape through the outlet. As a result, less than a complete charge of fluid is dispensed from the pumping chamber.
In similar fashion, existing domes require a relatively large amount of force to collapse the dome. When larger and smaller pump output is desired, the size of the dome must be increased to keep optimum pump efficiency constant as measured by compression ratio and the ratio of dead space to the dome internal volume. This is of particular concern, when a customer requests a different output because the ancillary pump components must also change size in order to accommodate the larger dome. Most times, however, compromises in performance are accepted over changing these components.
To account for the relatively large force needed to compress the domes, most dispensers incorporate a lever that provides a mechanical advantage to allow the user to pump soap from the dome. In hands free dispensers, larger or more batteries must be supplied to provide sufficient power with a minimally acceptable battery life.
As a result, there is a need for a diaphragm pump that requires relatively less force to dispense soap than existing dome pumps. There is a further need for a dome pump that collapses in a repeatable consistent fashion.
Further considering the issue of pump efficiency, another source of inefficiency is the currently used “floating” ball inlet check valve. The floating ball inlet check valve is provided at the inlet to prevent fluid from going back into the bottle when the dome is depressed. The floating ball rests in an open position allowing soap to fill the chamber beneath the dome, and closes in response to the pressure applied to the dome. As the ball floats toward the closed position, some soap leaks back through the inlet into the bottle. As a result, less than a complete charge of fluid is pumped from the chamber. Therefore, a better valve at the inlet would be desirable.
The floating ball design has additional disadvantages in that since it rests in an open position, the floating ball is prone to sticking after it rests for a period of time. Moreover, in terms of manufacture the floating ball design adds complexity to the pump assembly in terms of adding a component, namely the ball, providing inlet geometry that holds the ball in place, and, in assembly by adding the step of inserting the ball within the inlet. Consequently, a pump assembly that eliminates the floating ball inlet valve is desirable.